(a) Field of the Invention
The present invention relates to a liquid crystal display and a manufacturing method of a liquid crystal display.
(b) Description of Related Art
A display device such as a liquid crystal display (LCD) includes a plurality of pixels arranged in a matrix, and each pixel includes a transparent pixel electrode for displaying images. The pixel electrodes are driven by signals from signal lines including gate lines and data lines that intersect each other to define pixel areas and are connected to the pixel electrodes through switching elements such as thin film transistors (TFTs). The switching elements controls data signals from the data lines in response to scanning signals from the gate lines.
The LCD includes a TFT array panel including the signal lines, the pixel electrodes, and the TFTs and a common electrode panel including a common electrode facing the pixel electrodes and a black matrix having openings facing the pixel areas.
When a display area on a backplane for LCDs is too large to use an exposure mask, the entire exposure is accomplished by repeating a divisional exposure called step-and-repeat process. One divisional exposure unit or area is called a shot. Since transition, rotation, distortion, and etc. are generated during light exposure, the shots are not aligned accurately. Accordingly, parasitic capacitances generated between wires and pixel electrodes differ depending on the shots, and this causes the bright difference between the shots, which is recognized at the pixels located at a boundary between the shots. Therefore, the stitch defect is generated on the screen of the LCD due to brightness discontinuity between the shots.
In particular, a black matrix made of organic material, including black pigments, and having negative photosensitivity, which is also formed by divisional exposure, may cause stitch defects such as spots on an image. It is because the negative photosensitive organic material has different morphology depending on the number of the exposure to light. In detail, the boundaries of the shots overlap each other in consideration of alignment margin, and thus the portions of the negative photosensitive material on the boundaries of adjacent shots are twice exposed to light, while other portions within the shots are only once exposed to light. Therefore, the twice-exposed portions of the light blocking member have different morphology from other portions and this morphological difference cause different optical property, thereby yielding spots.